This project is fundamentally concerned with investigations designed to elucidate the following aspects of retinal function: (1) the specific relationship between intracellular potentials (neural, glial, and pigment epithelial), ionic fluxes, and extracellular field potentials so that the electroretinogram (ERG) and other retinal potentials might be unequivocally interpreted; (2) the interactions between neurons and glia, including cases in which retina excitability is altered (e.g., light-adaptation, or spreading depression) or through which significant field potentials are generated; (3) functional neuronal networks of the retina and their role in the visual process; (4) mechanisms of visual function which are specific to neuronal and glial interactions in each of the plexiform layers of the retina; (5) the cellular origin of intracellular responses as well as of intraretinally recorded spike discharges; and (6) the role of efferent and interplexiform cells in circadian rhythms of the vertebrate eye. Electrophysiological techniques for recording intra- and extra-cellular potentials will be combined with methods for measuring ionic fluxes (ion selective microelectrodes) and for computing current source densities in order to explore stimulus-dependent mechanisms for retinal function. The retina of the mudpuppy will be used because of its comparatively larger cells which offer an opportunity to quantitatively relate the activity of preganglionic cells to the retinal output via optic nerve fibers. The retinas of the frog, tiger salamander, and lizard will also be used as required for selected observations. It is expected that this work will aid in clarifying questions concerning the origin of ERG components and thereby further the interpretative utility of the ERG in clinical ophthalmological diagnoses. This research will also contribute to a more comprehensive view of the functional organization of the vertebrate retina, and to an understanding of mechanisms linking the activity of nerve and glial cells.